This invention relates to turbochargers for supplying relatively high pressure charge air to an internal combustion engine. More particularly, this invention relates to an improved electronically responsive control for adjusting wastegate valve position to control turbocharger operation.
Turbochargers are well known in the prior art, and typically comprise a turbine wheel and a compressor wheel mounted on a common shaft and carried within an appropriate housing. The housing adjacent the turbine wheel includes a gas inlet and a gas outlet, and is coupled to the engine exhaust gas manifold for circulation of the exhaust gas through the turbine engine housing to rotatably drive the turbine wheel. In turn, the turbine wheel rotatably drives the compressor wheel which compresses ambient air and supplies the compressor, pressurized air to the intake manifold of the engine.
The use of turbochargers is highly advantageous when compared with conventional naturally aspirated engines in that substantially higher density fuel air mixtures may be delivered to the engine cyclinders. This increased fuel air density results in substantially improved engine performance and efficiency. Turbocharger controls are typically included, for example, to limit the boost pressure of pressurized air delivered to the engine intake manifold.
One type of turbocharger control typically comprises a valved apparatus, commonly referred to as a wastegate valve, for bypassing a portion of the engine exhaust gases around the turbine wheel. In this manner a portion of the exhausted gases is prevented from driving the turbine wheel so that the turbine wheel rotates at less than maximum speed such that the compressor wheel is also driven less than maximum speed. Structurally, some of these bypass devices comprise a bypass passage integrally cast as part of the housing, along with a bypass or wastegate valve mounted within this bypass passage.
With the advent of digital electronic controls for controlling operation of an internal combustion engine, a variety of fast response control signals responsive to a variety of engine operating parameters are fed to a primary electronic control unit which develops electronic control systems for adjusting, for example, fuel flow, spark advance and timing, as well as a variety of other engine operating control systems. Yet most wastegate controls include pneumatic actuators responsive to engine pressure such as intake manifold pressure.
In automotive applications, it is important that the control system for a turbocharger be relatively simple, economical and, importantly, quite rugged for the relatively extreme environment presented by the turbocharger system.